English
For any a in P, the inverse of the lid map sends a to 1 ⊗ a; i.e., (lid R P).symm a = 1 ⊗ a.
Русский
Для любого a ∈ P обратное отображение lid отправляет a в 1 ⊗ a; то есть (lid_R P).symm a = 1 ⊗ a.
LaTeX
$$$ (\mathrm{Coalgebra.TensorProduct.lid}\; R\; P)^{\mathrm{symm}}(a) = 1 \otimes a. $$$
Lean4
/-- The base ring is a right identity for the tensor product of coalgebras, up to
coalgebra equivalence. -/
protected noncomputable def rid : M ⊗[R] R ≃ₗc[S] M :=
{ AlgebraTensorModule.rid R S M with
counit_comp := by ext; simp
map_comp_comul := by
ext x
dsimp
simp only [one_smul]
hopf_tensor_induction comul (R := S) x with x₁ x₂
simp }